This invention generally relates to a method and apparatus for taking a rock core drilling sample. In particular, the invention is directed to an improved method of taking core samples from base rock at any depth using simple elements in a controlled and reliable fashion. Some preferred embodiments of this invention are particularly useful for removing rock core samples in extraterrestrial environments.
Some current core sample removal techniques consist of drilling completely through the base rock in order to obtain a core sample. It is often impractical to drill completely through the rock to be sampled. The depth of the base rock may not be known, or if it is known, may be far deeper than the desired sampling depth.
Some current core sample removal techniques consist of drilling to a desired depth and rocking the drill shaft back and forth until the core sample cracks away from the base rock. When obtaining a core sample by drilling to the desired depth and rocking the drill shaft back and forth, several problems arise. The cutting annulus must be great enough to provide sufficient movement of the drill shaft as it is rocked back and forth. As the cutting annulus size increases, the drill tends to operate slower, work less efficiently, and generate more dust. If the drill depth is several times greater than the drill diameter, the cutting annulus must be further increased so as to provide the same rocking angle. Soon it becomes impractical to use this method of core sample removal at any depth greater than several drill diameters. Drill shaft flexing will also detract from the available rocking angle.
Some current core sample removal techniques apply relatively large external loads to the drill shaft which must react to ground. Some current core sampling techniques can therefore become difficult in sandy or soft surroundings. Additionally, in extraterrestrial environments, many of the weight, power, and cost restraints make undesirable a drilling apparatus requiring such external loads reacting to ground.
Some current core sample removal techniques subject the core sample to strong, rotational friction forces while drilling, which can result in inadvertent, premature core breakage. These premature breakages can cause the core sample to become jammed within the collection device. Additionally, the rotational friction forces against the core sample may cause particles to break off of the core sample and accumulate as dust. This dust may clog different parts of the drilling and core removal apparatus rendering either certain parts inoperable or possibly rendering the entire drilling and core removal apparatus inoperable.
Some current core sample removal techniques do not provide for a drill bit quick-change mechanism. In order to change the drill bit, often the entire drilling and core removal apparatus must be removed from the hole and changed using extra equipment. Some current core sample removal techniques run the risk of having the drill tube or possibly the entire drilling mechanism rendered inoperable and immobile if the drill bit gets clogged, broken, or otherwise stuck while still in the hole. Additionally, in extraterrestrial environments, the drilling and core removal apparatus is often attached to an autonomous research platform with other pieces of scientific equipment. If the drill bit were to become stuck in the hole it was drilling and no drill bit quick-change mechanism were available to release the drill bit while it remained within the hole, then the entire research platform may be rendered immovable and many of the pieces of scientific equipment may be rendered immobile and thus inoperable.
Some current core sample removal techniques provide a quick-change means for the drill bit, but are unable to obtain the core sample if the drill bit must be released during a drilling operation.
Some current core sample removal techniques do not provide for a stable bushing support to the drill bit during the drilling process.
Some current core sample removal techniques are not reliable enough to be run autonomously. Reliable and autonomous core sample removal techniques are particularly necessary in extraterrestrial environments.
Some current core sample removal techniques also require a large number of moving parts in order to achieve the drilling, core removal, core ejection, and drill bit changing actions. The large number of moving parts can increase the cost of the mechanisms, impart a loss of drilling efficiency, increase the cost of necessary repairs, and increase the downtime required for repairs. Additionally, in extraterrestrial environments, such a large number of moving parts may be unable to comply with weight, power, and cost restrictions.